Vibrational Raman and infrared spectroscopy are used to probe the dynamical, conformational, functional and thermodynamic properties of both model and intact membrane assemblies. Emphasis is placed on elucidating lipid-lipid and lipid-protein interactions within the bilayer aggregate. For example, model bilayer systems were reconstituted with several synthetic peptide paradigms for modeling human lung surfactant. The synthetic peptides consisted of residues 59-81 of human surfactant protein SP-B and twenty-one amino acid residue peptides containing repeating units of arginine separated by either four or eight leucines. Raman spectroscopic data demonstrated that the membrane bilayer order induced by constraints resulting from the interaction of charged amino acid residues with acidic bilayer lipids are critical features of a functionally successful lung surfactant. A novel approach has been developed for characterizing the redox, spin and conformational states of cytochrome oxidase by simultaneously determining the resonance Raman vibrational spectra and optical absorption spectra as a function of a potentiometrically controlled solution potential. As an adjunct, the first potentiometric titration of ferricytochrome c monitored by resonance Raman spectroscopy was determined. We are developing a novel spectroscopic imaging technique which combines the spatial resolving power of optical spectroscopy with the sensitivity and selectivity of vibrational spectroscopy. Using a commercial optical microscope, state-of-the-art acousto-optic devices and an extremely low light level imaging detector, our instrument should be capable of diffraction limited spatial resolution for both Raman scattering and near-infrared absorption spectroscopic microscopy.